The present invention relates, in general, to substrate structures, and more particularly, to substrate structures having improved heat dissipation capabilities.
Conventionally, electronic solid-state devices are formed in semiconductor substrates such as disk-shaped silicon wafers. Typically, many identical devices are formed in the surface of a wafer. After the devices are formed, the wafer is typically cut into individual dies each die comprising a single device.
Modern applications for the solid-state devices formed in wafers require increasingly higher power devices. For example, applications in telecommunications require high power radio frequency amplifiers. Additionally, as digital microprocessors become more complex they require higher power.
The higher power of the modern devices directly results in an increase in the creation of heat during the operation of the devices. The heat created by the devices must be dissipated in order for the devices to maintain acceptable operating temperatures.
A typical approach to dissipating heat from a semiconductor device is attachment to a heat sink which can efficiently conduct heat away from the device. Common heat sinks comprise metal such as copper, which is naturally a good heat conductor. Unfortunately, the typical semiconductor device will not operate properly if an electrical conducting material such as copper is directly attached to it. Consequently, in the past, individual die comprising individual semiconductor devices have been attached to ceramic substrates which are then attached to a metal heat sink. The ceramic substrate provides electrical isolation (insulation) between the semiconductor device and the metal heat sink. Unfortunately, the ceramic substrates are not particularly efficient in conducting heat away from the semiconductor device to the heat sink. An additional approach which has been taken is to thin the semiconductor substrate in which the electronic device is formed in order to minimize the amount of semiconductor material through which the heat must pass, since the heat is generated at the surface of the substrate where the device is formed. The thinned substrate may then be separated into individual die and attached to ceramic insulators and heat sinks as discussed above. Unfortunately, the substrates can not be thinned as much as desirable because they become subject to breaking during further processing.
Consequently, what is needed is a method for forming a semiconductor structure with improved heat dissipation. It would be desirable to provide electrical isolation without compromising heat dissipation. Additionally, it would be desirable to incorporate the electrical isolation and heat sinking while the wafer is still whole, rather than individually after dies have been separated out. This would significantly simplify processing and packaging. Additionally, it would be desirable to provide structural support to the semiconductor wafer so that it could be thinned to the very smallest thickness required for forming the electronic devices.